The present invention relates to units for filling containers, in particular bottles, with liquid or powder substances, in pharmaceutical field, e.g. medicines, or in cosmetics, e.g. perfumes.
More in particular, the present invention relates to a distributor for controlled filling of containers by checking the weight of the substance introduced therein.
It is known that it is necessary to respect strict weighing principles while filling bottles or containers with e.g. medicines, since the introduced substance must have a precise weight or volume.
Consequently, the tolerances admitted during containers filling and batching steps are very restricted. It is therefore necessary to verify the weight of containers coming out from the filling station.
According to this procedure, sample containers are selected from the conveying line at selected time intervals and weighed.
If the container weight does not fall within the admitted tolerance, the product quantity delivered at the filling station is adjusted.
After having been removed from the conveying line and weighed, the sample container is rejected.
The sample containers must be rejected, because difficulties and constructive problems of suitable operating means, which allow to recycle the rejected containers, have not been resolved yet.
The statistical weighing technique allows to weigh the containers very precisely out of the conveying line, however, it does not allow their reintroduction in the productive cycle.
Moreover, since the check is performed on statistical basis, it is possible that, after being packaged and sealed, the weight of some containers does not fall within the admitted tolerances.
According to another method, used at present, the containers are weighed directly on the conveying line, at the outlet of the station for filling the containers.
The conveying line features, arranged in predetermined positions and at predetermined space intervals, suitable weighing stations positioned in the regions of indentations or breaks of the conveying line.
Although this weighing method allows to check the weight of all containers coming out of the filling station, on the conveying line, it presents some operation problems with the detection of the containers actual weight.
The positioning of the weighing stations directly on the conveying line, which must move forward with a predetermined speed to maintain best production rate, can cause some weighing problems due to inertia.
Actually, it is difficult for the containers to get settled and steady in the weighing station within a time sufficient to acquire a precise measure.
An operation unit for feeding containers which allows to feed containers along a conveying line and to transfer them from the conveying line to a weighing station, situated along the conveying line, is disclosed in the Italian Patent Application No. BO2000A 000147 of the same Applicant.
The main object of the present invention is to propose a distributor unit, which allows to avoid the problems occurring in the prior art, and more precisely, a distributor unit, which allows to weigh the substance introduced into the containers in an extremely precise and effective way.
Another important object of the present invention is to propose a distributor unit which enables to weighing all the containers, completely clear of the conveying line, and reintroducing the weighed containers thereto.
A further object of the present invention is to propose a distributor unit, which rejects containers, whose weight does not fall within the admitted tolerance.
The above mentioned objects are obtained, in accordance with the contents of the claims, by a liquid substance distributor unit including:
a conveying line, which moves forward stepwise, so as to convey containers in a forward direction;
at least one filling unit, where said containers are filled with a
liquid substance;
at least one weighing station, associated to said conveying line;
said distributor unit (D) being characterized in that said weighing station includes, in combination:
at least one first weighing station, situated upstream of said filling unit with respect to said forward direction (Z) of said line, so as to weigh the containers before filling;
at least one second weighing station, situated downstream of said filling unit, with respect to said forward direction of said line, so as to weigh containers after filling;
a control unit, interfaced with said first weighing station and with said second weighing station, so as to acquire the weight of said containers, respectively before and after filling, and determine the net weight of the substance introduced in each container;
with each one of the above mentioned first and second weighing stations including:
a first weighing group and a second weighing group situated on opposite sides of said conveying line;
at least one weighing area for each of said first weighing group and second weighing group, for weighing a container conveyed by the conveying line;
at least one transfer group for transferring, during a conveying line stop, containers to be weighed from said conveying line to the weighing area of said second weighing group, and for transferring, at the same time, an already weighed containers from the first weighing group to said conveying line;
said transfer group transferring, during a next stop of said conveying line, further containers to be weighed from said conveying line to the weighing area of said first weighing group, and transferring at the same time, an already weighed containers from said weighing area of said second weighing group to said conveying line.